Vehicle not charging after 12v battery replaced

Last Sunday, I bought my second BMW i3—a 2015 Rex with 72k miles. The price was great because the car had been parked for over three months, causing the 12V battery to die and triggering over 50 error codes.

I also own a 2015 Rex with 130k miles and previously experienced a similar situation when the fuel pump relay failed. In that case, the main battery drained to 0%, which also depleted the 12V battery. My solution was to replace the 12V battery and leave it on a charger until fully charged, which brought everything back to normal.

With this new i3, however, replacing the 12V battery didn’t resolve the issues. The malfunctions still appeared on the screen, and the car wouldn’t take a charge. The charger shows EV connected, the charge port light is solid white, and the instrument panel shows it as plugged in, but the battery level doesn’t change at all.

Here’s what I’ve done so far:

Before purchasing, I saw a post about the car and asked the owner a few questions. He wasn’t very familiar with i3s but mentioned that the car was drivable before he parked it. He had tried to jump-start it with a NOCO jump starter, but that didn’t work.

On Sunday, I brought a new TX24HL battery, replaced the 12V battery, and the car powered on. However, the main battery still showed 0%, and the cooling fan was running at maximum RPM. Since there was no extension cord available to charge it in the parking lot, I decided to take a chance and tow it home, where I could swap parts with my other i3 to troubleshoot further.

Once I got it home, I plugged it into my Level 2 charger and noticed the 12V battery had died again. When I removed the battery, I realized it was already 15 months old, even though it was brand new from Advance Auto Parts. I replaced it on Monday morning with another battery that was only three months old.

I charged this new battery to 13.11V, reinstalled it, and waited for a new Level 1 charger to arrive (I had to return the U-Haul trailer, and the car isn’t drivable, so I couldn’t unload it in my garage).

After about two hours, the new charger arrived, and I saw that the main battery level had risen to 47%, which seemed like a positive development. However, when I plugged in the charger, the same issue persisted: the charger showed EV connected, the charge port light stayed solid white, the instrument panel showed it as plugged in, but the battery level didn’t increase.

I tried clearing the error codes with BimmerLink, but over 40 codes wouldn’t clear. I also used an OBD reader, but the codes returned after clearing. I left it on the charger for 10 hours, but nothing changed.

By the end of the day, I checked the 12V battery again, and it showed 12.06V. I removed it, recharged it to 12.64V, and reinstalled it this morning before leaving. I’m hoping there might be some improvement by the time I get home tonight.

Given this situation, does anyone have any suggestions on what else I could try?

Level1 charger is fairly slow.
Did you leave the level1 charger on it for two days or just a few hours to see a battery level increase?

Mine has same faults battery show 100% but says estimated range 6 miles

Frank-Li said:

Last Sunday, I bought my second BMW i3—a 2015 Rex with 72k miles. The price was great because the car had been parked for over three months, causing the 12V battery to die and triggering over 50 error codes.

I also own a 2015 Rex with 130k miles and previously experienced a similar situation when the fuel pump relay failed. In that case, the main battery drained to 0%, which also depleted the 12V battery. My solution was to replace the 12V battery and leave it on a charger until fully charged, which brought everything back to normal.

With this new i3, however, replacing the 12V battery didn’t resolve the issues. The malfunctions still appeared on the screen, and the car wouldn’t take a charge. The charger shows EV connected, the charge port light is solid white, and the instrument panel shows it as plugged in, but the battery level doesn’t change at all.

Here’s what I’ve done so far:

Before purchasing, I saw a post about the car and asked the owner a few questions. He wasn’t very familiar with i3s but mentioned that the car was drivable before he parked it. He had tried to jump-start it with a NOCO jump starter, but that didn’t work.

On Sunday, I brought a new TX24HL battery, replaced the 12V battery, and the car powered on. However, the main battery still showed 0%, and the cooling fan was running at maximum RPM. Since there was no extension cord available to charge it in the parking lot, I decided to take a chance and tow it home, where I could swap parts with my other i3 to troubleshoot further.

Once I got it home, I plugged it into my Level 2 charger and noticed the 12V battery had died again. When I removed the battery, I realized it was already 15 months old, even though it was brand new from Advance Auto Parts. I replaced it on Monday morning with another battery that was only three months old.

I charged this new battery to 13.11V, reinstalled it, and waited for a new Level 1 charger to arrive (I had to return the U-Haul trailer, and the car isn’t drivable, so I couldn’t unload it in my garage).

After about two hours, the new charger arrived, and I saw that the main battery level had risen to 47%, which seemed like a positive development. However, when I plugged in the charger, the same issue persisted: the charger showed EV connected, the charge port light stayed solid white, the instrument panel showed it as plugged in, but the battery level didn’t increase.

I tried clearing the error codes with BimmerLink, but over 40 codes wouldn’t clear. I also used an OBD reader, but the codes returned after clearing. I left it on the charger for 10 hours, but nothing changed.

By the end of the day, I checked the 12V battery again, and it showed 12.06V. I removed it, recharged it to 12.64V, and reinstalled it this morning before leaving. I’m hoping there might be some improvement by the time I get home tonight.

Given this situation, does anyone have any suggestions on what else I could try?View attachment 1580View attachment 1581View attachment 1583View attachment 1584

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Hey
I had similar MADNESS with an i8

Not same car but same designers brains

My impossible to fix, not charging, bot running, low 12v was cured very simply.

In the in and outs of the 12v battery of the i8..... A heavy large unit sitting in a fixed battery case..... I screwed it up without realizing.

I know all about i3 12volt units. I have 4 i3 cars these last 7 years. They are very different to i8 BUT may have the tiny wire that has to fit into the red battery terminal plastic underneath. This tiny wire is a safety shunt that says car has not crashed or ir upside down

This wire is so insignificant noone ever mentions it.

Please check your +ve battery terminal and wires and ensure you not left one dangling.

On the i8 it's a tiny short black wire with molded end looking like a leftover loom piece of unimoirtabce.

Once re plugged in to underneath of RED PLASTIC the car was REBORN.

GOOD LUCK LOOKING. There is so little room around 12v in the i3

Frank-Li said:

Last Sunday, I bought my second BMW i3—a 2015 Rex with 72k miles. The price was great because the car had been parked for over three months, causing the 12V battery to die and triggering over 50 error codes.

I also own a 2015 Rex with 130k miles and previously experienced a similar situation when the fuel pump relay failed. In that case, the main battery drained to 0%, which also depleted the 12V battery. My solution was to replace the 12V battery and leave it on a charger until fully charged, which brought everything back to normal.

With this new i3, however, replacing the 12V battery didn’t resolve the issues. The malfunctions still appeared on the screen, and the car wouldn’t take a charge. The charger shows EV connected, the charge port light is solid white, and the instrument panel shows it as plugged in, but the battery level doesn’t change at all.

Here’s what I’ve done so far:

Before purchasing, I saw a post about the car and asked the owner a few questions. He wasn’t very familiar with i3s but mentioned that the car was drivable before he parked it. He had tried to jump-start it with a NOCO jump starter, but that didn’t work.

On Sunday, I brought a new TX24HL battery, replaced the 12V battery, and the car powered on. However, the main battery still showed 0%, and the cooling fan was running at maximum RPM. Since there was no extension cord available to charge it in the parking lot, I decided to take a chance and tow it home, where I could swap parts with my other i3 to troubleshoot further.

Once I got it home, I plugged it into my Level 2 charger and noticed the 12V battery had died again. When I removed the battery, I realized it was already 15 months old, even though it was brand new from Advance Auto Parts. I replaced it on Monday morning with another battery that was only three months old.

I charged this new battery to 13.11V, reinstalled it, and waited for a new Level 1 charger to arrive (I had to return the U-Haul trailer, and the car isn’t drivable, so I couldn’t unload it in my garage).

After about two hours, the new charger arrived, and I saw that the main battery level had risen to 47%, which seemed like a positive development. However, when I plugged in the charger, the same issue persisted: the charger showed EV connected, the charge port light stayed solid white, the instrument panel showed it as plugged in, but the battery level didn’t increase.

I tried clearing the error codes with BimmerLink, but over 40 codes wouldn’t clear. I also used an OBD reader, but the codes returned after clearing. I left it on the charger for 10 hours, but nothing changed.

By the end of the day, I checked the 12V battery again, and it showed 12.06V. I removed it, recharged it to 12.64V, and reinstalled it this morning before leaving. I’m hoping there might be some improvement by the time I get home tonight.

Given this situation, does anyone have any suggestions on what else I could try?View attachment 1580View attachment 1581View attachment 1583View attachment 1584

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Ok

Here is what I know.

I have 3 of i3S and 2 of i8

See all sorts of error codes and ALWAYS it's the 12v battery giving problems

On the i8 there is a tiny black wire, insignificant short thing that plugs into a hole underneath the red battery plastic terminal cover. You can easily miss it. I don't know if i3 is same.

LOOK HARD at all the wires to 12v on positive side to ensure EVERY ONE is plugged to somewhere

This wire on i8 gives exactly same non charging symptoms as you describe

It tells if car has had a crash or is upside down and basically cuts off HV supply.

Noone ever talks about it. Drove me insane for a month researching everywhere until a very inquisitive neighbor said.... WHAT'S THIS LITTLE WIRE.
I said it's probably nothing.... spare..... but it was ESSENTIAL.

i3 Battery is so badly placed I'm sure you could easily miss connecting something when it's in and out many times.

You need 3 or 4 arms

GOOD LUCK

My i8 is totally cured in 4 long weeks and then 5 minutes

Harold M said:

On the i8 there is a tiny black wire, insignificant short thing that plugs into a hole underneath the red battery plastic terminal cover. You can easily miss it. I don't know if i3 is same.

LOOK HARD at all the wires to 12v on positive side to ensure EVERY ONE is plugged to somewhere

Click to expand...

Harold M said:

i3 Battery is so badly placed I'm sure you could easily miss connecting something when it's in and out many times.

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The i3's 12V battery positive cable clamp also includes an explosive connection that disconnects during a significant collision. This opens a relay in the HV battery pack that eliminates the high-voltage electrocution threat and prevents an i3 from remaining in or entering drive ready state.

During the many times that I have removed and installed 12V batteries in our i3's over 11 years, no wire has ever disconnected from this positive cable clamp. There are a couple of small wires connected to this clamp, but maybe they're permanently connected without a connector that could be unplugged.

Harold M said:

You need 3 or 4 arms

Click to expand...

I haven't found removing and installing the 12V battery to be overly challenging. Removing the frunk box is easy. I always remove the windshield washer fluid reservoir filler tube (rotate, pull up) to improve access. I remove the negative cable and the hold-down bracket, lift the battery out of the battery box, rotate it so the positive cable is closer to the front of the car, slide it out far enough to remove the positive cable clamp easily, and then slide it the rest of the way out. It really helps that it's small and relatively light. The lithium iron phosphate (LFP) battery that I now use is 1/3rd the weight of the AGM battery which makes removal and installation even easier.

The riskiest part is dropping the top battery hold-down bracket attachment screw. I've now added a thin plastic washer on the back side of this bracket through which this screw is threaded. This prevents the screw from falling out of the bracket when the bracket is being removed or installed.

alohart said:

The lithium iron phosphate (LFP) battery that I now use is 1/3rd the weight of the AGM battery which makes removal and installation even easier.

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I was going to ask how that battery holds up to the cold but now that I see your location I'm guessing you don't have much experience with that.

unL33T said:

I was going to ask how that battery holds up to the cold but now that I see your location I'm guessing you don't have much experience with that.

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Correct! However, there is a more expensive version of this LFP battery that includes a battery cell heater to allow it to work well in a cold climate according to its manufacturer.

alohart said:

Correct! However, there is a more expensive version of this LFP battery that includes a battery cell heater to allow it to work well in a cold climate according to its manufacturer.

Click to expand...

Link? Might look at that in 4 years when I'm due again. Although I have a hard enough time with the HV battery taking an hour to warm up, may not want to deal with that with the 12V.

When I looked into lithiums for the 12V before I only found 1 person saying they tried it for awhile and then it totally stopped working in a pretty short amount of time. I do run one in my motorcycle already but it goes away once the snow hits.

unL33T said:

Link? Might look at that in 4 years when I'm due again. Although I have a hard enough time with the HV battery taking an hour to warm up, may not want to deal with that with the 12V.

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I believe that a LFP battery should not be charged below 32 ºF but discharging isn't a problem. I am able manually disable charging and/or discharging of my LFP battery, so the model with the cell heater could disable charging automatically below 32 ºF while allowing the battery to provide power to the 12V system so the car could be used immediately. The cell heater would then heat the cells as one drives eventually allowing charging. The DC-DC converter provides all power needed while an i3 is in drive ready state, so the 12V battery shouldn't discharge much. That's just my guess as I don't have the model with the cell heater and don't live where it would be needed. A LFP battery for a Rivian truck is the correct size.

A set of SAE battery posts would need to be attached with UNF 10-32 screws. Those on the OEM AUX18L battery won't fit and are attached with M6 screws. I used a set of Tesla Model S posts. Some brass must be ground off 2 sides of each post base so that they will fit down in the recess in the case surrounding the terminals. A couple of brass washers should be placed in the voids on the undersides of the posts so that power can pass through these washers rather than only through the stainless steel attachment screws. So this isn't a plug-and-play solution…

unL33T said:

When I looked into lithiums for the 12V before I only found 1 person saying they tried it for awhile and then it totally stopped working in a pretty short amount of time.

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I have been running an Ohmmu G1DC22 LFP battery since November, 2023, with no problems. I have begun managing its charge level which should increase its life expectancy by disabling charging until its charge level decreases to ~50% before enabling charging for a few minutes to increase its charge level. Otherwise, an i3 keeps this battery at almost a 100% charge level at all times which isn't ideal for LFP longevity.

alohart said:

The i3's 12V battery positive cable clamp also includes an explosive connection that disconnects during a significant collision. This opens a relay in the HV battery pack that eliminates the high-voltage electrocution threat and prevents an i3 from remaining in or entering drive ready state.

During the many times that I have removed and installed 12V batteries in our i3's over 11 years, no wire has ever disconnected from this positive cable clamp. There are a couple of small wires connected to this clamp, but maybe they're permanently connected without a connector that could be unplugged.

I haven't found removing and installing the 12V battery to be overly challenging. Removing the frunk box is easy. I always remove the windshield washer fluid reservoir filler tube (rotate, pull up) to improve access. I remove the negative cable and the hold-down bracket, lift the battery out of the battery box, rotate it so the positive cable is closer to the front of the car, slide it out far enough to remove the positive cable clamp easily, and then slide it the rest of the way out. It really helps that it's small and relatively light. The lithium iron phosphate (LFP) battery that I now use is 1/3rd the weight of the AGM battery which makes removal and installation even easier.

The riskiest part is dropping the top battery hold-down bracket attachment screw. I've now added a thin plastic washer on the back side of this bracket through which this screw is threaded. This prevents the screw from falling out of the bracket when the bracket is being removed or installed.

Click to expand...

Thanks for these details. You describe perfectly the process of replacing the 12v what many have posted on You Tube - HOWEVER - I'm I interested in more detail regarding this: "The lithium ion phosphate (LFP) battery that I now use is 1/3rd the weight of the AGM battery..." Can the Rivan Ohmmu actually replace the Deka OEM for BMW?

mtkkk45 said:

Thanks for these details. You describe perfectly the process of replacing the 12v what many have posted on You Tube - HOWEVER - I'm I interested in more detail regarding this: "The lithium ion phosphate (LFP) battery that I now use is 1/3rd the weight of the AGM battery..." Can the Rivan Ohmmu actually replace the Deka OEM for BMW?

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The OEM battery weighs ~18 lb. while the Rivian LFP battery weighs ~6 lb. Basically, lithium, atomic weight 7, is much lighter than lead, atomic weight 207.

The Rivian LFP battery's open circuit resting voltage is ~0.5V higher than the OEM battery, and its output voltage doesn't decrease nearly as rapidly as its charge level decreases, so its voltage remains much higher than the OEM battery over its entire charge level range. Because of this, less current is required for the same output power, so its effective usable capacity is probably about double that of the OEM battery.

A negative is its higher initial cost assuming that its battery cell heater works well in cold weather. If it lasts considerably longer than the OEM battery, its lifetime cost could be less, but I don't know how long it would last. Also, it's not quite plug-and-play, and installing it before the i3's warranty expires could result in a battle with a dealer should a warranty claim be made.

One issue is that lithium battery cells degrade more rapidly when they remain at a high charge level. The i3's 12V battery charging system keeps the 12V battery fully charged almost all the time. The LFP battery manufacturer suggested that I could extend the battery's life by preventing its charge level from remaining high at all times. I do this by disabling charging using the Ohmmu smartphone app connected to the battery via Bluetooth. When the battery's internal voltage decreases below 13.0V as displayed in the Ohmmu app, I enable charging for several minutes while the DC-DC converter is on to increase its charge level. I do this every week or two.

alohart said:

The OEM battery weighs ~18 lb. while the Rivian LFP battery weighs ~6 lb. Basically, lithium, atomic weight 7, is much lighter than lead, atomic weight 207.

The Rivian LFP battery's open circuit resting voltage is ~0.5V higher than the OEM battery, and its output voltage doesn't decrease nearly as rapidly as its charge level decreases, so its voltage remains much higher than the OEM battery over its entire charge level range. Because of this, less current is required for the same output power, so its effective usable capacity is probably about double that of the OEM battery.

A negative is its higher initial cost assuming that its battery cell heater works well in cold weather. If it lasts considerably longer than the OEM battery, its lifetime cost could be less, but I don't know how long it would last. Also, it's not quite plug-and-play, and installing it before the i3's warranty expires could result in a battle with a dealer should a warranty claim be made.

One issue is that lithium battery cells degrade more rapidly when they remain at a high charge level. The i3's 12V battery charging system keeps the 12V battery fully charged almost all the time. The LFP battery manufacturer suggested that I could extend the battery's life by preventing its charge level from remaining high at all times. I do this by disabling charging using the Ohmmu smartphone app connected to the battery via Bluetooth. When the battery's internal voltage decreases below 13.0V as displayed in the Ohmmu app, I enable charging for several minutes while the DC-DC converter is on to increase its charge level. I do this every week or two.

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Thank you, Alohart. Assuming your warranty isn’t still in play and jeopardized, in addition to the Blue tooth access you have to your Ohmmu battery can you also adjust battery specs that are set for the Aux18 on the internal i3 computer and adjust these 12v specs to Ohmmu specs using bimmerfest interface to access onboard presets?

mtkkk45 said:

Assuming your warranty isn’t still in play and jeopardized, in addition to the Blue tooth access you have to your Ohmmu battery can you also adjust battery specs that are set for the Aux18 on the internal i3 computer and adjust these 12v specs to Ohmmu specs using bimmerfest interface to access onboard presets?

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The original 4-year general warranty is still in effect, so I hope not to have to claim a warranty repair before it expires.

The Ohmmu smartphone app does not support changing the LFP battery's capacity to 20 Ah to match that of the OEM AGM battery. It also does not support mimicking an AGM battery, so it performs like a 22 Ah LFP battery, ~0.5 V higher maximum open circuit resting voltage and much flatter voltage vs. charge level curve, which is quite different from a 20 Ah AGM battery.

The i3 electronic controller that controls 12 V charging recognizes only AGM and flooded-cell lead acid battery types, not LFP. It also recognizes only certain 12 V battery capacities like 20 Ah, 40 Ah, and higher. So I can't change the parameter values using BimmerCode to match my LFP battery. I think that this would be a bigger deal in a BMW with an alternator whose performance is adjusted based on the battery type, capacity, and age.

An i3 keeps its 12 V battery fully charged most of the time which could shorten the life of a LFP battery according to its manufacturer. I also suspect that this might also explain the short lives of the AGM battery for many i3 owners. Without a 12 V starter motor, the 12 V battery is never "exercised". The 12V batteries in Gen. 1 Honda Insights that didn't have a 12 V starter motor failed earlier than expected. Some owners began exercising their 12 V batteries periodically by purposely discharging them to ~50% by leaving high-beam headlights and the climate control system on full blast while the car was shut off so the DC-DC converter could not charge the 12 V battery. I don't know whether this increased the life expectancy of their 12 V batteries, but it was an interesting theory that might have some truth to it. Because of this, I have been managing the charge level of my LFP 12 V battery so that its charge level ranges from ~50% to 100%.

alohart said:

The original 4-year general warranty is still in effect, so I hope not to have to claim a warranty repair before it expires.

The Ohmmu smartphone app does not support changing the LFP battery's capacity to 20 Ah to match that of the OEM AGM battery. It also does not support mimicking an AGM battery, so it performs like a 22 Ah LFP battery, ~0.5 V higher maximum open circuit resting voltage and much flatter voltage vs. charge level curve, which is quite different from a 20 Ah AGM battery.

The i3 electronic controller that controls 12 V charging recognizes only AGM and flooded-cell lead acid battery types, not LFP. It also recognizes only certain 12 V battery capacities like 20 Ah, 40 Ah, and higher. So I can't change the parameter values using BimmerCode to match my LFP battery. I think that this would be a bigger deal in a BMW with an alternator whose performance is adjusted based on the battery type, capacity, and age.

An i3 keeps its 12 V battery fully charged most of the time which could shorten the life of a LFP battery according to its manufacturer. I also suspect that this might also explain the short lives of the AGM battery for many i3 owners. Without a 12 V starter motor, the 12 V battery is never "exercised". The 12V batteries in Gen. 1 Honda Insights that didn't have a 12 V starter motor failed earlier than expected. Some owners began exercising their 12 V batteries periodically by purposely discharging them to ~50% by leaving high-beam headlights and the climate control system on full blast while the car was shut off so the DC-DC converter could not charge the 12 V battery. I don't know whether this increased the life expectancy of their 12 V batteries, but it was an interesting theory that might have some truth to it. Because of this, I have been managing the charge level of my LFP 12 V battery so that its charge level ranges from ~50% to 100%.

Click to expand...

I am looking to pre-emptively change out my BMW 12V battery and upgrade as you have suggested. On the Ohmmu site the Rivian battery/s displayed suggest that the 'single' battery has the positive post on the BACK of the battery, not the front, as in the BMW battery. Is this your experience, and, if so, did this battery accept the Positive and Negative clamps as set up on the i3? (I note that you placed a Tesla post, but remain a bit confused, attempting to locate such a post on eBay; could you perhaps supply a picture or further clarify this essential adaptation?)
I love the BMS on the Ohmmu "app" and hope it may considerably delay the emotional turmoil that seems to attend battery deterioration in the i3! Thanks in advance, and for your expansion of the science of these great little cars!

Climber said:

On the Ohmmu site the Rivian battery/s displayed suggest that the 'single' battery has the positive post on the BACK of the battery, not the front, as in the BMW battery.

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I just looked at Ohmmu's Rivian battery installation video. The Ohmmu battery is shown with the positive terminal on the left rear, so when this battery is rotated front-to-back, its positive terminal would be right front like the i3's battery.

Climber said:

Is this your experience, and, if so, did this battery accept the Positive and Negative clamps as set up on the i3? (I note that you placed a Tesla post, but remain a bit confused, attempting to locate such a post on eBay; could you perhaps supply a picture or further clarify this essential adaptation?)

Click to expand...

Ohmmu was interested in selling a LFP battery for the i3 but had no i3 for installation testing. I volunteered to record an installation video in exchange for a LFP battery. I requested a Rivian battery because its dimensions are ideal for the i3. However, the unlabeled battery that I received is ½" taller than the Rivian battery and ⅜" taller than i3 OEM battery which made its installation more difficult. I later learned that this battery is a G1DC22 deep cycle battery, not a Rivian battery. This battery is much less expensive that the Rivian battery but might not include a battery cell heater. This isn't a problem in our tropical climate, but I suggest that no one who lives where freezing temperatures occur order a G1DC22 unless Ohmmu guarantees that it could be charged in below-freezing temperatures.

The i3 OEM battery's screw-on posts cannot be used with any Ohmmu battery, so Ohmmu sent me a set of Tesla Model S screw-on posts. These don't look like they'd fit the terminals on a Rivian battery and don't fit the flat G1DC22 terminals securely. I ground a bit of brass off two sides of the bases of these terminals so that they would fit into the recesses in the battery case surrounding the terminals. I filled the recesses on the undersides of these brass posts with 2 brass washers so that they would fit snugly against the terminals. Without making these modifications, the posts weren't securely attached to the terminals which could have resulted in poor electrical connections.

Climber said:

I love the BMS on the Ohmmu "app" and hope it may considerably delay the emotional turmoil that seems to attend battery deterioration in the i3!

Click to expand...

The BMS seems to keep charge level of the 4 cells well balanced. It is supposed to prevent overcharging, overheating, and other potential problems, and issue warnings when problems occur. I've not received any warnings, so can't comment on how well this works.

The BMS doesn't keep track of the charge level well. The BMS doesn't detect the low charging current of my 0.8 A battery charger, so it's not possible to stop charging before the battery is fully-charged. The displayed charge level remains constant until it's suddenly 100% because the battery's voltage increased to that of a fully-charged battery. When the charging current is high, the displayed charge level suddenly increases to 100% even though the actual charge level is lower.

Both charging and discharging can be enabled or disabled independently. I am currently manually preventing the charge level from remaining near 100% at all times to increase the battery's life expectancy. I disable charging for ~2 weeks which allows the charge level to gradually decrease when an i3 is off. The DC-DC converter provides 12 V power when an i3 is on. Unfortunately, the discharging current while an i3 is off is too low for the BMS to detect, so the displayed charge level doesn't decrease as it should. When the battery's output voltage decreases to 12.5 V, I enable charging for only a few minutes. It will charge at up to 55 A, so it doesn't take long to increase the charge level of this 22 Ah battery. Then I disable charging for another 2 weeks.

I am about to store our i3 for 101 days. I would normally disconnect the 12 V battery's negative cable. Instead, I am considering merely disabling discharging which would be much more convenient. I need to test this before we depart. Disabling discharging would have to decrease the battery's output voltage to 0 V to avoid the problems caused by spurious DTC's stored when the battery's output voltage is low but still >0 V.

I hope that the Ohmmu LFP battery has a longer life than an AGM battery, but it's still too soon to know.

If you decide to install an Ohmmu battery, send me a PM with your email address so that I can return some detailed modification and installation instructions and photos. Unfortunately, an Ohmmu battery isn't a plug-and-play solution.